Commit 6da957ad authored by Brendan Gregg's avatar Brendan Gregg

basic positional paramater support

parent 9e608df7
......@@ -253,8 +253,9 @@ Variables:
- `retval` - Return value from function being traced
- `func` - Name of the function currently being traced
- `probe` - Full name of the probe
- `curtask` - Current task_struct as a u64.
- `rand` - Random number of type u32.
- `curtask` - Current task_struct as a u64
- `rand` - Random number of type u32
- `$1`, `$2`, ... etc. - Positional parameters to the bpftrace program
Functions:
- `hist(int n)` - Produce a log2 histogram of values of `n`
......
......@@ -22,7 +22,6 @@ This is a work in progress. If something is missing, check the bpftrace source t
- [5. `? :`: ternary operators](#5---ternary-operators)
- [6. `if () {...} else {...}`: if-else statements](#6-if---else--if-else-statements)
- [7. `unroll () {...}`: unroll](#7-unroll---unroll)
- [Probes](#probes)
- [1. `kprobe`/`kretprobe`: Dynamic Tracing, Kernel-Level](#1-kprobekretprobe-dynamic-tracing-kernel-level)
- [2. `kprobe`/`kretprobe`: Dynamic Tracing, Kernel-Level Arguments](#2-kprobekretprobe-dynamic-tracing-kernel-level-arguments)
......@@ -45,6 +44,7 @@ This is a work in progress. If something is missing, check the bpftrace source t
- [6. `nsecs`: Timestamps and Time Deltas](#6-nsecs-timestamps-and-time-deltas)
- [7. `stack`: Stack Traces, Kernel](#7-stack-stack-traces-kernel)
- [8. `ustack`: Stack Traces, User](#8-ustack-stack-traces-user)
- [9. `$1`, ..., `$N`: Positional Parameters](#9-1--n-positional-parameters)
- [Functions](#functions)
- [1. Builtins](#1-builtins-1)
- [2. `printf()`: Print Formatted](#2-printf-Printing)
......@@ -909,6 +909,7 @@ That would fire once for every 1000000 cache misses. This usually indicates the
- `curtask` - Current task struct as a u64
- `rand` - Random number as a u32
- `cgroup` - Cgroup ID of the current process
- `$1`, `$2`, ..., `$N`. - Positional parameters for the bpftrace program
Many of these are discussed in other sections (use search).
......@@ -1155,6 +1156,73 @@ __libc_start_main+231
Note that for this example to work, bash had to be recompiled with frame pointers.
## 9. `$1`, ..., `$N`: Positional Parameters
Syntax: `$1`, `$2`, ..., `$N`
These are the positional parameters to the bpftrace program, also referred to as command line arguments. If the parameter is numeric (entirerly digits), it can be used as a number. If it is non-numeric, it must be used as a string in the `str()` call. If a parameter is used that was not provided, it will default to zero for numeric context, and "" for string context.
This allows scripts to be written that use basic arguments to change their behavior. If you develop a script that requires more complex argument processing, it may be better suited for bcc instead, which supports Python's argparse and completely custom argument processing.
One-liner example:
```
# bpftrace -e 'BEGIN { printf("I got %d, %s\n", $1, str($2)); }' 42 "hello"
Attaching 1 probe...
I got 42, hello
```
Script example, bsize.d:
```
#!/usr/local/bin/bpftrace
BEGIN
{
printf("Tracing block I/O sizes > %d bytes\n", $1);
}
tracepoint:block:block_rq_issue
/args->bytes > $1/
{
@ = hist(args->bytes);
}
```
When run with a 65536 argument:
```
# ./bsize.bt 65536
Attaching 2 probes...
Tracing block I/O sizes > 65536 bytes
^C
@:
[512K, 1M) 1 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
```
It has passed the argument in as $1, and used it as a filter.
With no arguments, $1 defaults to zero:
```
# ./bsize.bt
Attaching 2 probes...
Tracing block I/O sizes > 0 bytes
^C
@:
[4K, 8K) 115 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[8K, 16K) 35 |@@@@@@@@@@@@@@@ |
[16K, 32K) 5 |@@ |
[32K, 64K) 3 |@ |
[64K, 128K) 1 | |
[128K, 256K) 0 | |
[256K, 512K) 0 | |
[512K, 1M) 1 | |
```
# Functions
## 1. Builtins
......
......@@ -16,6 +16,10 @@ void Builtin::accept(Visitor &v) {
v.visit(*this);
}
void PositionalParameter::accept(Visitor &v) {
v.visit(*this);
}
void Call::accept(Visitor &v) {
v.visit(*this);
}
......
......@@ -38,6 +38,14 @@ public:
void accept(Visitor &v) override;
};
class PositionalParameter : public Expression {
public:
explicit PositionalParameter(long n) : n(n) { is_literal = true; }
long n;
void accept(Visitor &v) override;
};
class String : public Expression {
public:
explicit String(std::string str) : str(str) { is_literal = true; }
......@@ -260,6 +268,7 @@ class Visitor {
public:
virtual ~Visitor() { }
virtual void visit(Integer &integer) = 0;
virtual void visit(PositionalParameter &integer) = 0;
virtual void visit(String &string) = 0;
virtual void visit(Builtin &builtin) = 0;
virtual void visit(Call &call) = 0;
......
......@@ -20,6 +20,20 @@ void CodegenLLVM::visit(Integer &integer)
expr_ = b_.getInt64(integer.n);
}
void CodegenLLVM::visit(PositionalParameter &param)
{
std::string pstr = bpftrace_.get_param(param.n);
if (bpftrace_.is_numeric(pstr)) {
expr_ = b_.getInt64(std::stoll(pstr));
} else {
Constant *const_str = ConstantDataArray::getString(module_->getContext(), pstr, true);
AllocaInst *buf = b_.CreateAllocaBPF(ArrayType::get(b_.getInt8Ty(), pstr.length() + 1), "str");
b_.CreateMemSet(buf, b_.getInt8(0), pstr.length() + 1, 1);
b_.CreateStore(b_.CreateGEP(const_str, b_.getInt64(0)), buf);
expr_ = buf;
}
}
void CodegenLLVM::visit(String &string)
{
string.str.resize(string.type.size-1);
......
......@@ -28,6 +28,7 @@ public:
{ }
void visit(Integer &integer) override;
void visit(PositionalParameter &param) override;
void visit(String &string) override;
void visit(Builtin &builtin) override;
void visit(Call &call) override;
......
......@@ -12,6 +12,12 @@ void Printer::visit(Integer &integer)
out_ << indent << "int: " << integer.n << std::endl;
}
void Printer::visit(PositionalParameter &param)
{
std::string indent(depth_, ' ');
out_ << indent << "builtin: $" << param.n << std::endl;
}
void Printer::visit(String &string)
{
std::string indent(depth_, ' ');
......
......@@ -11,6 +11,7 @@ public:
explicit Printer(std::ostream &out) : out_(out) { }
void visit(Integer &integer) override;
void visit(PositionalParameter &param) override;
void visit(String &string) override;
void visit(Builtin &builtin) override;
void visit(Call &call) override;
......
......@@ -18,6 +18,24 @@ void SemanticAnalyser::visit(Integer &integer)
integer.type = SizedType(Type::integer, 8);
}
void SemanticAnalyser::visit(PositionalParameter &param)
{
param.type = SizedType(Type::integer, 8);
std::string pstr = bpftrace_.get_param(param.n);
if (is_final_pass()) {
if (!bpftrace_.is_numeric(pstr)) {
if (!call_ || call_->func != "str")
/*
* call_ was added just for this test: ensuring a string parameter is
* only used inside str(). Without it, string parameters used as
* integers would return their buffer address. Maybe that's ok?
* If this behavior is changed, codegen needs to support it.
*/
err_ << "$" << param.n << " used numerically, but given \"" << pstr << "\". Try using str($" << param.n << ")." << std::endl;
}
}
}
void SemanticAnalyser::visit(String &string)
{
if (string.str.size() > STRING_SIZE-1) {
......@@ -109,6 +127,9 @@ void SemanticAnalyser::visit(Builtin &builtin)
void SemanticAnalyser::visit(Call &call)
{
// needed for positional parameters context:
call_ = &call;
if (call.vargs) {
for (Expression *expr : *call.vargs) {
expr->accept(*this);
......
......@@ -19,6 +19,7 @@ public:
out_(out) { }
void visit(Integer &integer) override;
void visit(PositionalParameter &param) override;
void visit(String &string) override;
void visit(Builtin &builtin) override;
void visit(Call &call) override;
......@@ -60,6 +61,7 @@ private:
bool check_alpha_numeric(const Call &call, int arg_num);
Probe *probe_;
Call *call_;
std::map<std::string, SizedType> variable_val_;
std::map<std::string, SizedType> map_val_;
std::map<std::string, MapKey> map_key_;
......
......@@ -392,6 +392,31 @@ std::vector<uint64_t> BPFtrace::get_arg_values(std::vector<Field> args, uint8_t*
return arg_values;
}
bool BPFtrace::is_numeric(std::string str)
{
int i = 0;
while (str[i]) {
if (str[i] < '0' || str[i] > '9')
return false;
i++;
}
if (i == 0)
return false;
return true;
}
void BPFtrace::add_param(const std::string &param)
{
params_.emplace_back(param);
}
std::string BPFtrace::get_param(int i)
{
if (i > 0 && i < params_.size() + 1)
return params_[i - 1];
return "0";
}
void perf_event_lost(void *cb_cookie, uint64_t lost)
{
printf("Lost %lu events\n", lost);
......
......@@ -68,6 +68,9 @@ public:
std::string resolve_probe(uint64_t probe_id);
uint64_t resolve_cgroupid(const std::string &path);
std::vector<uint64_t> get_arg_values(std::vector<Field> args, uint8_t* arg_data);
void add_param(const std::string &param);
bool is_numeric(std::string str);
std::string get_param(int index);
std::string cmd_;
int pid_{0};
......@@ -99,6 +102,7 @@ private:
int ncpus_;
int online_cpus_;
std::vector<int> child_pids_;
std::vector<std::string> params_;
std::unique_ptr<AttachedProbe> attach_probe(Probe &probe, const BpfOrc &bpforc);
int setup_perf_events();
......
......@@ -78,6 +78,7 @@ pid|tid|cgroup|uid|gid|nsecs|cpu|comm|stack|ustack|arg[0-9]|retval|func|probe|cu
"||" { return Parser::make_LOR(loc); }
"+" { return Parser::make_PLUS(loc); }
"-" { return Parser::make_MINUS(loc); }
"$" { return Parser::make_DOLLAR(loc); }
"*" { return Parser::make_MUL(loc); }
"/" { return Parser::make_DIV(loc); }
"%" { return Parser::make_MOD(loc); }
......
......@@ -107,6 +107,11 @@ int main(int argc, char *argv[])
}
}
if (argc == 1) {
usage();
return 1;
}
if (bt_verbose && (bt_debug != DebugLevel::kNone))
{
// TODO: allow both
......@@ -140,23 +145,14 @@ int main(int argc, char *argv[])
if (script.empty())
{
// There should only be 1 non-option argument (the script file)
if (optind != argc-1)
{
usage();
return 1;
}
// Script file
char *file_name = argv[optind];
err = driver.parse_file(file_name);
optind++;
}
else
{
// Script is provided as a command line argument
if (optind != argc)
{
usage();
return 1;
}
err = driver.parse_str(script);
}
......@@ -172,6 +168,12 @@ int main(int argc, char *argv[])
BPFtrace bpftrace;
// positional parameters
while (optind < argc) {
bpftrace.add_param(argv[optind]);
optind++;
}
// defaults
bpftrace.join_argnum_ = 16;
bpftrace.join_argsize_ = 1024;
......
......@@ -60,6 +60,7 @@ void yyerror(bpftrace::Driver &driver, const char *s);
LOR "||"
PLUS "+"
MINUS "-"
DOLLAR "$"
MUL "*"
DIV "/"
MOD "%"
......@@ -99,6 +100,7 @@ void yyerror(bpftrace::Driver &driver, const char *s);
%type <ast::ExpressionList *> vargs
%type <ast::AttachPointList *> attach_points
%type <ast::AttachPoint *> attach_point
%type <ast::PositionalParameter *> param
%type <std::string> wildcard
%type <std::string> ident
......@@ -161,6 +163,8 @@ pred : DIV expr ENDPRED { $$ = new ast::Predicate($2); }
ternary : expr QUES expr COLON expr { $$ = new ast::Ternary($1, $3, $5); }
;
param : DOLLAR INT { $$ = new ast::PositionalParameter($2); }
block : "{" stmts "}" { $$ = $2; }
| "{" stmts ";" "}" { $$ = $2; }
;
......@@ -181,6 +185,7 @@ expr : INT { $$ = new ast::Integer($1); }
| STRING { $$ = new ast::String($1); }
| BUILTIN { $$ = new ast::Builtin($1); }
| ternary { $$ = $1; }
| param { $$ = $1; }
| map { $$ = $1; }
| var { $$ = $1; }
| call { $$ = $1; }
......
......@@ -42,6 +42,7 @@ TEST(Parser, builtin_variables)
test("kprobe:f { func }", "Program\n kprobe:f\n builtin: func\n");
test("kprobe:f { probe }", "Program\n kprobe:f\n builtin: probe\n");
test("kprobe:f { args }", "Program\n kprobe:f\n builtin: args\n");
test("kprobe:f { $1 }", "Program\n kprobe:f\n builtin: $1\n");
}
TEST(Parser, map_assign)
......
......@@ -64,6 +64,7 @@ TEST(semantic_analyser, builtin_variables)
test("kprobe:f { retval }", 0);
test("kprobe:f { func }", 0);
test("kprobe:f { probe }", 0);
test("kprobe:f { $1 }", 0);
test("tracepoint:a:b { args }", 0);
// test("kprobe:f { fake }", 1);
}
......@@ -661,6 +662,13 @@ TEST(semantic_analyser, probe_short_name)
test("i:s:1 { 1 }", 0);
}
TEST(semantic_analyser, positional_parameters)
{
// $1 won't be defined, will be tested more in runtime.
test("kprobe:f { printf(\"%d\", $1); }", 0);
test("kprobe:f { printf(\"%s\", str($1)); }", 0);
}
} // namespace semantic_analyser
} // namespace test
} // namespace bpftrace
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